If you get there upto 2 hours early, at the auto check in booth that you drive up to,
It will ask you if you would like an earlier crossing, (if available)
If you choose yes, then check the letter they are calling on the overhead gantry as you drive to the parking area, If your letter is shown continue to the holding/loading area
If not park up and rest/look round shops until your letter is called
Don,t worry if you try to go to the train too early they will just ask you to go back into the parking area
I usually go to the holding area as soon as I can
Depending on time of crossing, there is a tea bar situated in the holding/loading area, Selling drinks and snacks, There are also toilets in the holding area
Alan H